Always listen for FP on alternateBouncer showing

Fixes: 268183230
Test: manually test by launching camera over a secure
lock screen with side FP enrolled. try to access
the (locked) camera roll, see alternate FP bouncer and
successfully authenticate from the alternate bouncer
Test: atest KeyguardUpdateMonitorTest

Change-Id: Ic59067f5cdada0ff99b1e8e5e78539ee9ec04e34